Semiconductor devices are widely and commonly used in the construction of electronic circuits for many types of electronic products. The manufacturing of a semiconductor device typically involves growing a cylindrical-shaped silicon (or other base semiconductive material) ingot. The ingot is sliced into circular flat wafers. Through a number of thermal, chemical, and physical manufacturing processes, active semiconductor devices and passive devices are formed on one or both surfaces of the wafer. The wafer is cut into individual rectangular semiconductor die which are then mounted and attached to a leadframe, encapsulated, and packaged as discrete or integrated circuits. The packaged discrete and integrated circuits are mounted to a printed circuit board and interconnected to perform the desired electrical function.
The active and passive semiconductor devices and associated structures are formed in part by either growing or depositing layers of material on the wafer surface. The growing process usually involves oxidation and nitridation. The depositing process may involve chemical vapor deposition (CVD), evaporation, or sputtering. In the typical CVD process, the wafer is placed in a CVD reaction chamber, e.g. tube furnace. The reaction chamber receives a controlled flow of a specific reactant chemical or precursor. The reaction chamber also receives an energy source, such as heat, induction RF, radiant, plasma, or ultraviolet, to induce a chemical reaction within the chamber. Inside the chamber, the atoms and molecules of the precursor chemical are mixed and reacted in the presence of the energy source to form a gas or vapor. The atoms from the vapor settle upon, i.e. are physically deposited on, the wafer surface to form a solid product or thin film from some component(s) of the precursor. During nucleation, the first few atoms of the chemical vapor come to rest in a uniform random distribution on the wafer surface. The deposited atoms then grow from small islands to larger islands. As more atoms are deposited, the islands merge together to coalesce into a continuous transition film having a thickness of hundreds of angstroms. The transition film grows into a bulk thin film having amorphous, single crystalline, or polycrystalline structure. The thickness of the bulk thin film is controlled by the reactant chemical flow, energy source, and duration of the reaction.
The layers of material deposited by CVD can form insulators and dielectrics (silicon dioxide, silicon nitrides), conductors (aluminum, aluminum-silicon alloys, aluminum-copper alloys, barrier metals, refractory metals, doped polysilicon), and semiconductor regions (epitaxial silicon and poly silicon) for the active and passive semiconductor components and devices. In some high speed and high density semiconductor processes, such as ultra-large-scale integrated (ULSI) circuits, it is desirable to deposit low-resistivity metals such as Cu, Ru, Pt, Ir, W, TiN, TaN, WCxNy, and TaSixNy on the wafer surface for use as high speed interconnects, barrier layers, and contact electrodes. In the CVD process, the metal thin film may be deposited over substantially the entire surface of the wafer. In later steps, the undesired portions of the metal thin film are removed by etching and cleaning, leaving the metal thin film in the desired locations. The etching process to remove the undesired metal thin film adds manufacturing costs and increases the chance of etch-induced damage.
A need exists for a manufacturable selective-CVD process which eliminates the post-CVD etching step to remove excess material, with its associated cost and potential for etch-induced damages.